An innovative fluorescence system for sensing biomolecular interactions was developed in Phase I that is based on total internal reflection fluorescence (TIRF). The main advantages of this system are integrated microfluidics and a design that allows rapid replacement of TIRF sensor chip. The feasibility of building a highly sensitive and versatile TIRF biosensor instrument was successfully demonstrated in Phase I. In Phase II, we will design and build a complete turn-key TIRF instrument. The proposed instrument will be equipped with integrated fluidics, an automated sample handling module and a precision mechanism for rapid replacement of TIRF sensor chips. A variety of inexpensive TIRE sensor chips enclosed in cartridges will be available for convenient immobilization of different biomolecules. In this manner, the TIRF biosensor instrument will be designed for routine investigation of biomolecular interactions. During year one of Phase II, we propose to build five units of the TIRF biosensor instrument. In year two, the TIRF instrument will be tested in laboratories of our consultants and in our own lab. At the end of Phase II a fine-tuned industrial prototype wilt be obtained. The TIRF biosensor instrument will be constructed and tested in close collaboration with C&L Instruments and our consultants. A TIRF biosensor instrument is a much-needed tool for studies related to structural genomics, proteomics and other fields where detailed knowledge of biomolecular interactions are important. Since the proposed instrument will transform difficult TIRF experiments into routine measurements, the TIRF biosensor has the potential to revolutionize studies in many fields, including cancer research, biomaterials studies, drug discovery, cell signaling, genomics and proteomics, nanotechnology, immunoassay and vaccine development.